Poison glands are puffy pockets behind each ear of a toad. Their purpose is to defend the toad against predators. When captured, the toad will squirt poison, from the poison glands, at potential predators. This toxic substance is why dogs spit out toads soon after picking them up. While the poison won't kill a dog, it does taste very bitter. It is also one of the reasons you should wash your hands after handling toads.